I'll try to embellish and not to repeat the good advice that others have already offered.

I've done several panel interviews in my career. They're not that bad. Panel interviews are sort of like having a converstaion with a group. And they're a bit like doing a public speaking engagement.

Your candidate should be prepared for a general overview of what the company is like and what they're most interested in having in a person for that position and a person in their organization. A few practice situations will be helpful. But the candidate should keep in mind that this is a conversation. And she wants to gather information about these people. She should be prepared to do some amount of listening.

As with public speaking, eye contact is very important. When one panelist asks a question, answer them. However, it is helpful to then include the others with eye contact as the content of the response is developed. This can also be done as some small embellishment of the direct answer is provided.

She may want to do a sound check of the room so that she'll have some idea of the acoustics. Easy to do. Simply make some company- or interview-related comment as she enters the room. This will show whether the sound echoes, gets gobbled up, or requires little effort in projection.

One tactic I used during all of my competition speaking was to find the one person in the room who had the most hostile facial and body language. I would then direct most of my energy toward winning that person over by getting them to drop the "closed" stance. My attention was given to all the members of the room [my competitors and the judge], but the hostile party got more play -- not the judge. By the end of my 5-10 minute speech, it was accomplished. I always took 1st or 2nd place in all of my competition speaking.

Animation in the voice is good. Encourage her to speak with enthusiasm mixed with thoughtfulness, and always, professionalism. Encourage her to be open and friendly. Excessive smiling indicates nervousness and subservience. Lose the grins.

I think panel interviews are an indication that there will be heavy public contact and a need to think on one's feet. You've inferred she has those strengths. Counsel her to be herself.

Remind her that this is an interview. She should have her own questions and ask the panel for clarification about matters that haven't been discussed but are part of what she will expect as part of the job [indicates knowledge of the position and expertise; ability to deliver if needed].

Instead of a one-on-one conversation, it's a group conversation.

As for the panelists' taking notes, you may want to encourage her to take notes (Why make her feel she's begging for the job?) so she'll remember what happened later and assist her in making a decision -- and for the follow-up thank you note.